Manufacture of lamps



4 July 16, l940- A. BONNEY, JR., ETAL 2,208,113

MANUFACTURE OF LAMPS Filed Feb. 27, 1937 2 Sheets-Shea?I l July 15, 940- A. BONNEY, JR., Ei- AL l 2,208,113

MANUFACTURE 0F LAMPS Filed Feb. 27, 1937 2 Sheets-Sheet 2 INVENTOR f4. 30AM/5) .\5. GMF/7N ATTORNEY Patented July 16, 1940 l UNITED STATES PATENT'IOFFICE 2,208,113 mancuernas or LAMPS Alfred Bonney, Jr., Verona, and Daniel S. Gustin, Bloomiield, N. J., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 27, 1937, Serial No. 128,156

l 14 claims. (ci. 11e-2) This invention relates to the manufacture of apparatus for introducing mercury into the lamp vlamps and, more particularly, to a method of exbulb. haust for gaseous discharge lamps which involves Fig. 7 is a vertical sectional view of the lamp a simplification of the schedule,and an improve.- after completion, except for basing, and also il.- ment in the quality of the product. lustratlng the nnal tipping off. A5

The principal object of our invention generally Referring to the drawings in detail, like parts considered is to manufacture electronic devices, being designated by like reference characters, such as high intensity mercury vapor lamps, there is shown a lamp 3 having a glass envelope while employing a simplified exhaust treatment l0, suitable for usein the manufacture of a high 1o which results in improvement in the `quality of intensity mercury vapor lamp. Said envelope has 10 the product. A main electrodes Il and I2, preferably coated ini- Another object of our invention is the heat tially with alkaline earth metal carbonatos, and treatment of lamps, or other electronic devices astarting electrode I3 sealed thereinto.v Leads to such as high intensity mercury vapor devices, said electrodes, in the present embodiment, are l5 when nlled with an inert gas at such a pressure brought out at one end of the envelope as lndi- 15 that the envelopes thereof can be madehotter cated at I4, I5, and I6, said leads being shown without deformation. covered with asbestos, or other heat insulating A further object of our invention is the manusleeves, in order to protect them during the manfacture of lamps comprising electrodes coated ufacturing operations. The envelope and enwith emission mixtures, such as alkaline earth closed electrodes and leads may be constructed 20 metal carbonates, on such as exhaust schedule like the corresponding parts of the device disthat said carbonates are at least partially declosed in the Gustin application Serial No. 75,745,

composed during the exhausting operation. led April 22, 1936, and owned by the assignee of A still further object of our invention is the the present application.

manufacture' of high intensity mercury vapor In order to allow for finally introducing a de- 25 lamps and other electronic devices, in which elec- Sired quantity of mercury into the envelope IU, trodes coated with emission mixtures are sealed there is PIOVided E Supplemental tube ll C0111- in vitreous vessels, on an exhaust schedule inmunicating with the envelope III by means oi an volving the filling of such vessels with an inert exhaust tube I8. Said supplemental tube congas, such as argon, and baking at higher than tains a glass or frangible capsule or pellet Il, 3o

. normal temperatures, made possible by the presholding the desired quantity 0f mercury, conence of said gas, so that not only is`a more efveniently held away from the exhaust tube i8 by fective heat treatment and degasication of the an inwardly extending bulge or contraction l in envelope and enclosed parts secured, but the the tube Il, and a ball or weight 20, for liberatemission mixtures are at 'least partially reduced ing the mercury from Said Capsule When desired. 35 to the desired form. The supplemental tube Il is in turn connected Other objects and advantages of the invention, to the exhaust manifold 2l by means of an exrelating to the particular arrangement and con-V haust tube 22. struction of the various parts, will become appar- After connection to the manifold 2I and preent by reference to the following description and liminery evacuation' through Open SOD COCkS 53 40 accompanying drawings in which: and 55, the lamp bulb I0 is desirably tested for Eig. l is an elevational view, partly in vertical leaks with a high-frequency eOl- If 110 leaks are section, of apparatus which may be employed in found, an inert gas, such for example, as prepracticing our invention, including an electricalpurified Genk aljgen gas, iS admitted by Opening ly heated oven. valves or stop cocks 23 and 24 and permitting the 45 Fig. 2 is an elevational view, looking from th ilow of gas from the supply pipe 25 until '160 m. m. left, of the apparatus shown in Fig. 1. pressure in the bulb II is indicated by the mer- Fig. 3 is a fragmentary view showing means cury seal 2l when the stop cock 28 is opened. for applying high frequency heating to a lamp. The desired pressure is shown when the level of Fig. 4 is a diagrammatic view `illustrating a the mercury in the tube 21 drops to the level of 50 lamp connected to a circuit for further treatment. the mercury in the pool 29.' 'I'he gauge 26 serves Fig. 5`is an elevational view illustrating a lamp to indicate only relatively low gas pressures. being initially tipped oli. v l The next step' in our exhaust method, after Fig. 6 is a fragmentary elevational view, shown shutting the stop cocks 23 and 24, is to raise the g partly in vertical section, and illustrating the individual oven 3l over the bulb Il. and tube Il 55 containing the mercury capsule and breaker, and bake about four minutes at a temperature preferably between 775 and 825 C., while the ventl through the stop cock 28 is left openv to the atmosphere, thereby avoiding the danger of excessive pressure. The baking temperature may be measured in any suitable manner, as by a thermo-couple, not shown, in the empty oven 30 at izle middle of the zone occupied by the lamp bulb Each oven 39 desirably comprises a refractory insulating tube 3l, wound with high resistance wire 32, with insulating material between the turns. The tube is desirably wound with a smaller number of turns per inch adjacent the upper portion than at the middle and lower portion, in order to equalize the temperature. 'I'he tube is desirably supported on a bottom asbestos disc 33 with its lower end portion fitting an upstanding boss thereof, inside of a casing 34, which `may be formed of galvanized iron. The disc 33 `is secured in place by Vclamping the galvanized iron casing 34 therearound by means of a bottom casting 35 tightened by means of a set screw 36'.

The space between the tubing 3| and the casing 34 is desira ly lled with refractory heat-insulating mate al 31, and the top of the annular space between/the tubing 3| and the casing 34 is closed by means of top asbestos disc 38. The top portion of the casing 34 isclamped to the disc 38 by means of topcasting 39, tightened by means 5, of a set screw 40. Energy is carried to the winding 32from the source of supply 4| through conductors 42 and 43,`variable resistance 44 being 'employed to regulate the heat of the furnace. Y

counterweight 48 connected thereto by means of a cable 49 passing Y over pulley 59, rotatablymounted on shaft 5I extending between the supporting rods 45, only one of which is illustrated. In this way the furnace `30 may be readilyV raised and lowered by means of handles 52, only one of which is illustrated, and will stay in any position desired.

After the lamp has been baked out, as heretofore described, the stop cock 28 is closed and the oven 30 dropped rapidly. As soon as the lamp bulb I0 loses visible redness, the stop cock 53 is opened to start exhausting said bulb. If the bulb is too cool when the mercury vacuum pump is opened, lamp quality will suffer due to reabsorption of gases by the lamp parts. If lthe bulb is too hot, it may collapse.

When the lamp bulb I0 coils clear indicating a good vacuum, all of the individual stop cocks 55 are desirably shut oil at the manifold, except that to the one bulb to be treated, and high frequency is applied to the lamp 9, as indicated in Fig. 3. by means of the coil 54. The power of the coil 54 is such that the electrode surrounded thereby reaches a bright yellow color at nal treatment. When high frequency is rst applied to an electrode. a bright flash of ionized gas is indicated momentarily. As soon as the electrode begins to be visibly red, this ionization disappears anda column of blue gas shows in the bulb III.

, This indicates that carbon dioxide is being generated from the electron emission material on the electrode undergoing treatment. Treatment should be continued until this gas disappears and the high-frequency coil 54 removed just as a very bright white ionization occurs around the electrode. It is important to discontinue treatment immediately the white ash occurs to avoid bulb discoloration.

The bottom electrode I2 and the auxiliary electrode I3, away'from the exhaust tube, are desirablyrst treated to reduce the reabsorption in treating the second main electrode II. In

order to complete the electrode treatment after treating the second electrode, we return the coil 54 to the first electrode I2, gradually raising the temperature to a bright yellow, but still using care to avoid bright white ionizationl ash of gas. As gas is driven off, a point is reachedwhen the supply o`f remaining gas flashes out in a` manner similar to that in avvacuumjtype incandescent lamp on ash aging. 'Ireatment should now be alternated between the electrodes until they show no further evolution of gas. y

After treating one lamp, its manifold stop cock 55 may be closed and the remaining lamps, if any, similarly treated with high frequency electric current by induction.

The lamp under treatment is then preferably connected to a 230-volt A. C. line 56, preferably in series with a reactance and variable resistance 51, or other means for obtaining-a current of 2 to 5 amperes, which may be indicated by ammeter A, as shown in Fig. 4. Inert gas, such as 18 to 20 m. m. of prepurified tank argon, is then admitted ythrough the stop cocks 23 and 24, and exhaust tube 22, and an arc through the lamp 9 started with spark coil at' about 41/2 amperes. The lamp should be burned about one minute at about 41/2 amperes, and the current then reduced to about 3 amperes for about two minutes. After this burning, the lamp should show a uniform milky-blue glow with a purple glow at each electrode'. The current is then reduced to about 2 amperes, cut oi, and the stop cock 55 immediately opened to the mercury pump and the lamp 9 exhausted to a clear coil.

The vacuum pump is then shut oif and inert gas, such as argon, again admitted through stop cocks 23 and 24 until atmospheric pressure is shown on the mercury column 21.

The stop cocks 23 and 24 are now desirably again shut oi and the oven raised over the lamp 9 and auxiliary tube I1 which are allowed to bake for vabout two minutes at a temperature of from 775 to 825 C., the vent through the mercury seal' 29 being left open to the atmosphere. After the lamp has been subjected to this second baking, the stop cock 23 to the mercury line is closed and the oven 30 dropped rapidly. As soon as the lamp loses visible redness, the vacuum line to the mercury pump is opened through the stop cocks 53 and 55. Similar precautions are to be observed as in connection with the exhausting after the rst baking.

When the lamp 9 coils clear, all the individual stop cocks 55 are preferably shut off at the manifold, except that to the one lamp being treated, and high frequency again applied, as4 indicated in Fig. 3, by means of the coil 54. The gas evolved by baking the parts is, of course, much less than in the first treatment and care should be taken to avoid bright ionization. As a iinal check, the high frequency coil should be rapidly alternated between the twonelectrodes, between the positions 54 and 54',as indicated in Fig. 3, allowing the electrode color to reach as near a bright yellow as possible, in order to catch evidence of the last traces of gas.

The lamp under treatment is then connected, as before, to a 23o-volt A. C. line 56, preferably in series with a reactan'ce and variable resistance f closing stop cock 53, and prepurifled tank argon gas admitted to a-pressure of from 7 to 9 m. m. ol' mercury after the lamp has' been cooled to about 60 C. The lamp is then again operated in the circuit, as shown in Fig. 4, at about 3 amperes, and if the color4 indicates that the gas `has been removed from the electrodes, the lamp may -be tipped ofi', as indicated in Fig. 5. It is not necessary to use liquid air traps in connection with the aforedescribed schedule. y

The lamp 9 is then desirably inverted so that the supplemental or capsule tube I1 extends downward, as shown in Fig. 6, and shaken up and down, or otherwise moved, so that the steel ball or weight 20 will strike the capsule I9 and break it. The capsule tube I'i and the end of the bulb I0 are then inserted in the electrically operated oven 30, as shown in Fig. 6, while the latter is heated to a temperature of from 350 to 400 C. 'I'he capsule tube I 'i is heated untilall the mercury is evaporated therefrom and condensed in the cool portion of the bulb I0, 4as indicated ai:l

58. Care'should be used to see that the vbulb is -.not cracked by too rapid heating, and that all the lead or support 60 to the electrode il to prevent .over heating. The lamp is then complete, except for the basing operation.

From the foregoing disclosure, it will be seen that we have described a method of'exhaust for gaseous discharge lamps in which the emission mixture and metal parts are treated at the same time the glass parts are degassed. This is made possible by heating the glass of the bulb while the same is filled with an inert gas, thereby making it possible to get the glass much hotter without deformation. The permissive gain in temperature by this method is approximately C., with a hard or high softening point material such as 172 glass now customarily used for mercury lamps, so that a temperature of from 775 to 825 C., may be employed. At this'temperature, highl enough to anneal the glass, carbonates of emission material are decomposed, at leastv inpart, thereby making it unnecessary to heat by lhigh frequency for as long a time.

necessity for liquid air traps is eliminated by this process which is equally eective for other electronic devices where emission mixtures are employed. It will, therefore, be seen that by so treating electronic devices, not only is the simplication of the exhaust-schedule permitted, but a' very decided improvement in quality results.

Although a preferred embodiment of our inar, scope of the appended claims.

1. The method of manufacturing electronic devices, comprising bulbs enclosing electrodes coated with the carbonates of alkaline earth metals, which comprises illling each bulb with argon at approximately atmospheric pressure, baking each bulb at such a temperature that the carbonates are partially decomposed, allowing each bulb to cool, exhausting each bulb, treating the electrodes in each bulb to further degasify them, admitting argon to each bulb, operating each device with a discharge current, exhausting .each bulb, repeating the admission of argon, baking and degasitlcation,V admitting argon at reduced pressure, operating each device with discharge,

current, introducing' mercury into each device, and tipping off.

2. The method of manufacturing high intensity mercury vapor lampscomprising iilling each lamp bulb with argon at approximately atmospheric pressure, baking each lamp, allowing 'each lamp to cool, exhausting each bulb, treateach lamp with a discharge current, introducing mercury into each lamp, and tipping oil.

3. The method of manufacturing high intensity mercury vapor lamps comprising filling each lamp bulb with argon at approximately atmospheric pressure, baking each lamp approximately four minutes at a temperature from 775 to 825 C., allowing each lamp to cool until it loses visible redness, exhausting each bulb, treating the electrodes in. each bulb with high frequency to degasify it, admitting from 18 to 20 m. m. of argon to each bulb, operating each lamp with a discharge current oi' about 41/2 amperes for about one minute, operating at about 3 amperes for about two minutes, reducing the current to 2 amperes, cutting on? the current, exhausting each bulb, repeating the admission of argon, baking, exhausting, and high-frequency degasiiication, admitting argon to a pressure of 7 to 9 m. m., operating each lamp with a discharge current of about 3 amperes, introducing the desired quantity of mercury into each lamp, and tipping oi.

4. An adjustable oven for baking lamps comprising a refractory insulating open ended tube differentially wound with high-resistance wire, whereby the terms are farther apart near the top to equalize the temperature, insulating material between the turns of said wire, means supporting said tube, comprising 'a disc carrying an upstanding boss around which the lower end portion of said tube lits, a metal casing enclosing said tube and supporting means, heat-insuj lating material between `said tube and casing,

means for closing the upper end of thel annular space between said tube and casing while leaving the upper end of the tube open, vertical supporting rods, means slidable over said rods and engaging upper and lower portions of said oven, a pulley, a counterweight, means extending from said counterweight over said pulley and secured to said oven for holding it in adjusted position, and means for energizing said winding for securing the desired temperature in said oven.

5. The method of manufacturing high-intensity mercury vapor lamps comprising disposing a lamp, including a bulb and electrodes, a tube containing mercury being connected thereto, above a vertically movable upwl rdly-opening even', counterweighd endadapted te alternatelly receive and be removed from said lamp, filling the bulb with argon at a desired pressure, moving said oven upwardly until it encloses said lamp,

energizing said oven to cause the lamp to be baked for a desired length of time at a suitable temperature lowering said oven to expose said lamp and allow it tocool until it loses visible redness, exhausting the lamp, treating the electrodes with high-frequency current for degasication purposes,'admitting argon into the bulb,

, lamp with a desired discharge current, applying the bulb, repeating the admission of argon, againA raising said oven to enclose said lamp and cause thesame tobe again baked, rrepeating the highfrequency degasication, again admitting argon at a desired pressure to the bulb, operating said the oven over the connected tubev containing mercury, 'in order to cause a desired amount of said mercury nto be introduced into said bulb,

k and tippingl off.

6. The method of manufacturing electronic devices comprising hard glassl bulbs enclosing electrodes which* carry alkaline earth metal car' bonates, including the step of lling, the lbulbs with an inert gas, applying heat externally to said bulbs to raise them to a degassing temperaturev in excess of 775 C., to soften the bulb material. and transform said carbonates tooxides, and admitting mercury thereto.

7. The method .of manufacturing electronicv devices which include hard glass bulbs enclosingv electrodes which carry alkaline earth metal carbonates, comprising lling said bulbs with inert gas at approximately atmospheric pressure, applying heat externally to said bulbs, while under atmospheric pressure to raise them to a degassing temperature in excess of 775 C., Yin order to anneal the bulb material and change said carbonates to oxides, and afterwards admitting a desired quantity of mercury thereto.

8. 'Ihe method of manufacturing electronic devices comprising bulbs enclosing electrod coated with carbonates of alkaline earth metals, which comprises lling each bulb with inert gas at approximately atmospheric pressure, baking each bulb, allowing to cool, exhausting, heating the electrodes to' effect degasification thereof, again admitting inert gas toeach bulb, operating each device with a discharge current, introducing mercury into each device, and tipping off.y

9. The method of manufacturing lamps, each l, including a bulb and electrodes coated with earth metal compounds, comprising exhausting each bulb, treating the electrodes with high frequency current in order to decompose the compounds and degasify them, admitting inert gas into said bulb, operating the lamp with a relatively high discharge for a predetermined length of time and then at a lower` dischargel for a greater length of time, further reducing the. current now through said lamp, terminating said current flow, exhausting the bulb, again admitting inert gas, baking said lamp, and., repeating the high frequenc'y degasification, v

10. The method of manufacturing electronic devices which employ hard glass bulbs andelectrodes comprising the carbonates of electron-y emission material, comprising lling said bulbs with an inert gas, and heating to a degassing temperature in excess of 775 C., so that said bulbs would deform if the gas were not present, whereby the added effect, of decomposing said carbonates to the desired oxides while the bulbs are degassed; is obtained.

-1l. 'Ihe method of manufacturing electronic 'devices which employ hard glass bulbs and electrodes comprising heat-decomposable lcompounds of electron-emission material, comprising ylling said bulbs with an inert gas at approximately atmospheric pressure, and degassing said bulbs by heating to .a temperature in excess of 775 C., so

that'they would deform if the gas were not present, thereby securing the added effect of decomposing said compbunds to the desired emission material while degassing.

12. The method of manufacturing electronic devices, Vcomprising hard glass bulbs enclosing emission mixtures, including the step of filling the bulbs with an inert gas, applying heat ex- I, n ternally to said bulbs to raise them to a temperatureih excess of 775 C., to soften and anneal said bulbs and simultaneously decomposesaid mixtures, and afterwards admitting mercury.

11j. The method of manufacturing electronic devices, which include emission mixtures' enclosed in hard glass vessels, Acomprising filling said vesselswith inert gas at approximately atmospheric pressure, applying heat externally to said vessels to raise them to a. temperature in excess of 775 C., to soften said vessels and simultaneously'eiect at least partial decomposition of said s mixtures, and admitting mercury there-I 14. The method of manufacturing an electronic device, which includes electrodes having alkaline earth metal carbonates thereon enclosed in a hard glass vessel, ,which comprises Yfilling said vessel with argon at approximately atmospheric pressure, applying heat externally to said 

